Bump and color data in a single brush?
Blender only paints to one image at a time.

One solution may be to set the texture brush mapping to stencil and align them visually. If your brush textures align and you don't move the 3dview then the two textures will just line up after you change brush settings and active layers.

When you enable stencil mapping, the texture is overlaid on the 3dview. Use  RMB to move the texture into place, &#8679; Shift  RMB to scale and &#9096; Ctrl  RMB to rotate, then use  LMB to paint it onto your texture image.